Work in proceeding on the development of new supports for solid-phase synthesis and the application of these for elaboration of oligonucleotide sequences. The supports consist of polylysine grafts extending from the surface of highly cross-linked polystyrene beads. Linker molecules join the amino side-chains of the lysine residues to the 3'-position of the 3'-terminal unit; cleavage is to give either the 3'-alcohol or 3'-phosphate product. Coupling reactions are based on the phosphotriester approach and trinucleotide blocks will be used for major build-up of the product sequence. The advantages proposed for our resins over those currently in use are several. The synthesis takes place in a polypeptide matrix, having similar solvation properties to those of the product oligonucleotides; the polystyrene core serves to retain good mechanical properties. Reagents do not have to diffuse to the interior of the bead so reaction conditions should stimulate homogeneous conditions, a situation ideal for the fragment coupling approach to synthesis. Linking reagents and blocking groups are proposed that should be highly stable during synthesis but highly frangible to fluoride ion. Also, work is starting on the use of readily available, inexpensive tetrazole derivatives that may prove useful in coupling reactions.